The Avengers #88

In "The Summons of Psyklop," the Avengers face their most bizarre challenge yet when the Hulk—finally contained by the combined genius of Reed Richards and Charles Xavier—is snatched mid-capture and whisked away by an ancient alien entity with a sinister agenda. With a mix of science, psychic power, and a touch of voo-doo, the heroes must track down the missing gamma-powered giant before the alien's dark rituals awaken something far older and more dangerous. Written by Roy Thomas and Harlan Ellison, with dynamic art by Sal Buscema and inks by Jim Mooney, this 1971 classic features a cover by Sal Buscema that captures the eerie, otherworldly tension of the story.